The instant invention relates to a process for piecing yarn on an open-end spinning device in which a fiber feeding device is turned on and whereby the produced fiber stream is deflected on its way to a fiber collection surface, and is removed until the actual piecing process is initiated, through the backfeeding of the yarn; whereupon the fiber stream is again deflected in synchronization with this backfeeding and is conveyed to the fiber collection surface. The invention also relates as well to a device to carry out the process.
A process of this type as well as a device to carry it out are known from the international patent application WO 86/01235, corresponding to U.S. Pat. No. 4,676,059. By means of this known process and device, it is intended to prevent the fibers which have suffered during the stoppage before the piecing process, from being guided into the spinning device, and to ensure that only fibers of perfect quality enter the spinning rotor. It has, however, been found to be extremely difficult to adapt yarn draw-off to the arrival of fibers, which takes effect suddenly in the spinning device after release of fiber feeding, so that the piecing joint deviates considerably in thickness from the normal yarn thickness. In order to remedy this disadvantage, it has been proposed, according to the above-mentioned patent application, to control the switch-over of the previously removed fiber stream gradually, so that the fiber stream becomes effective only gradually in the spinning device. However, a control device which is complicated, and must also be controlled with the utmost precision is required for this. It has also been shown that in practice, satisfactory results cannot be achieved in this way.